diff --git a/core/java/src/net/i2p/data/DataHelper.java b/core/java/src/net/i2p/data/DataHelper.java
index 72bfa1c37d..ac51f8128c 100644
--- a/core/java/src/net/i2p/data/DataHelper.java
+++ b/core/java/src/net/i2p/data/DataHelper.java
@@ -666,7 +666,7 @@ public class DataHelper {
      * @param value non-negative
      */
     public static void toLong(byte target[], int offset, int numBytes, long value) throws IllegalArgumentException {
-        if (numBytes <= 0) throw new IllegalArgumentException("Invalid number of bytes");
+        if (numBytes <= 0 || numBytes > 8) throw new IllegalArgumentException("Invalid number of bytes");
         if (value < 0) throw new IllegalArgumentException("Negative value not allowed");
 
         for (int i = offset + numBytes - 1; i >= offset; i--) {